The SHT-12 FS fixed transmitter is used for wireless transmission of switch signals. Counter pulses from light barriers or movement sensors are sent to the fixed transmitter and 1:1 to the receiver (e.g. an SHR-12 K1) by wireless transmission. The number of visitors to a building is then determined by the appropriate software or hardware. Turnstiles are no longer required and the customer can enter the building without being disturbed. As an option, the entrances can be closed at an adjustable maximum in order to control the visitor numbers automatically. In combination with an access control system, it is also possible to record personal data to maintain an overview of the visitors.